Delivery of anticancer drugs in a carrier could minimize damage to healthy tissues, prolong drug circulation time, and selectively accumulate drugs in tumors through enhanced permeability and retention (EPR) effect. Various carrier systems such as liposomes, quantum dots, and self-assembled nanoparticles or vesicles, have been reported in recent years. Amphiphilic polymers containing hydrophobic and hydrophilic segments can be readily self-assembled into nano-sized vesicles in aqueous solution. As one type of important self-assembled vesicles, polymersomes with stabilized structures have special capabilities of encapsulating guest molecules into their empty core domains and thus possess great potential for drug delivery.